query

The term query occurs in telecommunication, as well as in the checking of states, the query of search engines and above all in the targeted search in databases.

1. In programs, a query involves the retrieval of stored data (e.g. files or programs) with the aid of a query station. One speaks in this connection of the call operation, in a request response procedure. The situation is different in dialog mode, where the system signals the readiness of queries.
2. In telecommunications, polling involves the provision of calls by the terminal or switching equipment. Incoming calls that could not be routed to the subscriber can be queried by the subscriber in the query center.
3. In the case of search services on the Internet, query stands for a searchrequest to a search engine. Such a query is nothing else than entering the search term into the search field of the search engine. The query can be general or extended with search engine specific links.
4. In databases, query is understood as the targeted search for data in stored, structured or unstructured sources. Queries are most common in business intelligence( BI) and other business applications. They are central to database programming. A query is used to selectively extract data from a set of data. This data can then be read or modified. Both structured and unstructured data sets are possible as data sources. The table shows some examples and the typical queries.
   

   Structured and unstructured

   queries There are specialized programming languages for queries in information technology. The best known and most widely used are SQL and MDX. The Structured Query Language (SQL), pronounced "sequel" in English, is the standard language for relational database queries. Originally a pure query language, modern versions/derivatives such as Microsoft's Transact SQL or Oracle's PL/SQL are now full-fledged programming languages for data processing, though not for programming user interactions. MDX is a special language for querying OLAP cubes. Visually it is very similar to SQL, but it is quite unique and only suitable for OLAP. It is mainly used by Microsoft and Hyperion (Oracle).